We conditionally format version with VersionPrerelease in a number of
places. Add a package-level function where we can unify the version
format. Replace most of version formatting in terraform, but leave th
few instances set from the top-level package to make sure we don't break
anything before release.
* small doc update
* provider/atlas: Add docs for Artifact Data Source
* provider/atlas: Remove a test method that isn't used
* provider/atlas: Add Data Source for Atlas Artifact
* provider/atlas: Show deprecation error on atlas_artifact resource
James Bardin